Investigation of Nonionophoric Coccidiostat Residues in Feed as a Consequence of Carryover

Residues of nonionophoric coccidiostats at carryover concentrations in feedstuffs collected from feed mills or animal farms in central Italy were detected as part of the official controls carried out from 2011 through 2016. The 118 samples were collected on the production line or during feed distribution and storage to determine the sampling sites at major risk of cross-contamination. For determination of nonionophoric coccidiostats, a fast, easy, and cheap method was developed and validated. Feed samples were extracted with acetonitrile-methanol and directly injected for liquid chromatography with tandem mass spectrometry. A total of 24 samples (20.3%) were positive, but only 5 (4.2%) of these samples exceeded the maximum limit set by European legislation. Most of the positive samples were collected from a batch of feed produced immediately following processing of another batch to which the coccidiostat robenidine had been added.